I have one of those $8 Saleae clones off of ebay, and I have a proof of concept python script that calculates the right CRC.

I need to spend some time writing the actual sigrok plugin.

I was about to build a 6502 NOP adapter, but then read that the Atari signatures require a special counter instead built with 2 LS393s, as that increments the addresses once per clock, where as the NOP adapter requires two clocks so the signatures don't match. Though perhaps the plugin can simply have an option to skip every other clock.